Fugitive pattern assembly and method

ABSTRACT

A fugitive pattern assembly is made by preforming one or more fugitive patterns of an article to be cast, placing the preformed patterns in an injection die, and injecting fluid gating material into the die to form gating connected to the patterns. The fugitive patterns are disposed in end-to-end and/or side-by-side relation and are interconnected by the gating.

FIELD OF THE INVENTION

The present invention relates to a fugitive pattern assembly for usemaking a shell mold for the investment casting of metals and alloys aswell as a method and injection die for making a fugitive patternassembly.

BACKGROUND OF THE INVENTION

In the well known “lost wax” process of investment casting, a fugitiveor disposable wax pattern is made by injection molding melted wax orother fluid fugitive material in a die corresponding to theconfiguration of the article to be cast. A plurality of such moldedpatterns are joined to a common gating system made of wax or otherfugitive material, and/or to one another by gating, to provide a patternassembly that can be invested in a ceramic shell mold. For example, thegating system typically includes a sprue or runner to which one or morepatterns are connected and a pour cup connected to the sprue or runner.Multiple fugitive patterns may be joined by gating in end-to-end orother arrangement to one another before being joined to the gatingsystem. The actual configuration of the pattern assembly variesdepending on the type of cast article to be made in the shell mold; forexample, whether the cast article is to be an equiaxed grain,directionally solidified columnar grain, or single crystal casting.

Typically, as a result of complexity of the pattern assembly and/or costof injection dies, the patterns are joined to the gating system and/orto one another manually using labor-intensive techniques in a mannerthat requires a joint that is waterproof and structurally sound toprevent the patterns from separating from the gating system as the shellmold is built up on the pattern assembly. When the patterns and gatingsystem are made of wax, the patterns are joined to the gating system bywax welding processes well known in the art to produce a wax weld jointbetween the patterns and the gating system. However, manually assembledfugitive pattern assemblies can exhibit unwanted variability in patternlocations and joint quality from one pattern to the next and from onepattern assembly to the next.

The pattern assembly thus produced is invested in a ceramic shell moldby repeatedly dipping the pattern in a ceramic slurry, draining excessslurry, stuccoing with coarse ceramic particles or stucco, and airdrying until a desired thickness of a ceramic shell mold is built-up onthe pattern assembly. The pattern assembly then is removed from thegreen shell mold typically by heating the shell mold to melt out thepattern assembly, leaving a ceramic shell mold which then is fired atelevated temperature to develop appropriate mold strength for casting amolten metal or alloy.

An object of the invention is to provide an improved method of making afugitive pattern assembly, as well as the pattern assembly made by themethod, useful in making shell molds for the lost wax precisioninvestment casting process wherein the need for manual joining of thefugitive patterns to one another and/or to a gating system is reduced.

SUMMARY OF THE INVENTION

The present invention provides in one embodiment a method of making afugitive pattern assembly involving preforming a fugitive pattern of anarticle to be cast, placing the preformed pattern in an injection die,and injecting fluid gating material into the die to form in-situ gatingconnected to the pattern. Typically, a plurality of fugitive patternsare placed in the die and the fluid gating material is injected into thedie to form gating that interconnects the patterns.

In a particular embodiment of the invention, the fugitive patterns aredisposed in end-to-end relation and are interconnected by the gatingextending between end-to-end regions of adjacent patterns.

In another particular embodiment of the invention, the fugitive patternsare disposed in side-by-side relation and are interconnected by gatingextending between side-by-side end regions of adjacent patterns.

In practicing a particular method embodiment of the invention, thepattern is placed in a pattern-receiving cavity of the die. Thepattern-receiving cavity communicates to a gating cavity of the die. Thefluid gating material is injected into the gating cavity to form thegating in-situ in the die and connected to the pattern. The patternpreferably includes an extension that resides in the gating cavity ofthe die when the pattern is received in the pattern-receiving cavitysuch that the extension is captured in the in-situ formed gating. Thepattern extension includes a mechanical joint-forming surface, such as adovetail joint-forming surface, to provide a mechanical joint betweenthe pattern and gating.

The invention also provides a fugitive pattern assembly including afugitive pattern of an article to be cast and gating connected to thepattern by injecting a fluid gating material as described above. Thepattern assembly can include multiple fugitive patterns that aredisposed in end-to-end relation or side-by-side relation and areinterconnected by the injected gating.

In an illustrative embodiment, the patterns each have an airfoil regionwith a root region and a tip region wherein end-to-end root regions ofadjacent patterns are interconnected by the gating, end-to-end tipregions of adjacent patterns are interconnected by the gating, or theroot region of one pattern is interconnected to the tip region of anadjacent pattern by the gating. In another illustrative embodiment, thepatterns each have an airfoil with a root and a tip wherein end-to-endroots of adjacent patterns are interconnected by the gating and/orside-by-side tips of adjacent patterns are interconnected by the gating.

The invention further provides an injection molding die that includes apattern-receiving cavity and a gating cavity communicated to thepattern-receiving cavity for receiving fluid gating material to formgating in-situ and connected to a preformed pattern received in thepattern-receiving cavity. The die typically includes an injection runnerconnected to the gating cavity and through which fluid gating materialis introduced into the gating cavity.

Advantages of the invention will become more readily apparent from thefollowing detailed description.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a lower half of a gating injection die pursuantto an embodiment of the invention wherein airfoil patterns are joined inend-to-end relation with root extensions of the patterns joined togetherby the in-situ injected gating.

FIG. 1A is an elevational view of the pattern assembly produced usingthe gating die of FIG. 1.

FIG. 1B is a schematic side elevaton of lower and upper die halves ofthe gating die.

FIG. 2 is a plan view of a lower half of a gating injection die pursuantto another embodiment of the invention wherein airfoil patterns arejoined in end-to-end relation with a root extension of one patterninterconnected to a tip extension of an adjacent pattern by in-situinjected gating.

FIG. 2A is an elevational view of the pattern assembly produced usingthe gating die of FIG. 2.

FIG. 3 is a plan view of a lower half of a gating injection die pursuantto a further embodiment of the invention wherein airfoil patterns arejoined in side-by-side relation with the root extensions of the patternsjoined by a common gating runner.

FIG. 3A is an elevational view of the pattern assembly produced usingthe gating die of FIG. 3.

FIG. 4 is a plan view of a lower half of a gating injection die pursuantto a still further embodiment of the invention wherein airfoil patternsare joined in side-by-side relation with root extensions of the patternsjoined by a first common in-situ injected gating and with adjacent tipextensions of the patterns joined by a second common in-situ injectedgating.

FIG. 4A is an elevational view of the pattern assembly produced usingthe gating die of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method of making a fugitive patternassembly for use in the lost wax investment casting process employed inthe high volume commercial production of metal and alloy cast articleswherein a refractory (e.g. ceramic) shell mold is formed on the patternassembly to replicate its shape and the pattern assembly is subsequentlyremoved to leave an empty refractory shell mold for casting of the metalor alloy. The invention is described below for purposes of illustration,and not limitation, in relation to a fugitive pattern assembly for usein making a shell mold for investment casting of an airfoil, such as agas turbine engine blade or vane, although the invention is not limitedin this regard and can be practiced to make a pattern assembly for usein making a shell mold for the investment casting of any article. Theinvention is especially useful in making a pattern assembly having aplurality of wax patterns joined to a wax gating system, although theinvention can be practiced using any fugitive pattern material, such asconventional pattern wax, solid or foam plastic (e.g. polymeric foamsuch as polyurethane foam), polymeric pattern materials, and others.

FIG. 1 schematically shows an illustrative embodiment of the inventionfor making a pattern assembly wherein preformed fugitive airfoilpatterns 10 are to be joined in end-to-end (root-to-root) relation. Eachairfoil pattern comprises a root region 11, an airfoil region 12, and atip region 13. Such airfoil patterns 10 are used in making a shell moldfor the investment casting of gas turbine engine blades for example.

The airfoil patterns 10 can be injection molded in a conventionalpattern die (not shown) by injecting a fluid fugitive pattern material,such as molten wax, into a suitably configured cavity in the patterndie. For purposes of illustration and not limitation, the fugitivepatterns can be made using screw type injection molding machines, moltenwax pot injection presses, and other injection and/or press machineswherein a molten pattern material is introduced preferably underpressure into a mold cavity. Injection molded patterns are well knownand described for example in U.S. Pat. Nos. 6,497,272 and 6,505,672which are incorporated herein by reference. Those skilled in the artwill appreciate that the invention can be practiced using one or morefugitive patterns 10 that is/are formed using any suitable patternmaking process and apparatus and that the invention is not limited toinjection molding of the patterns.

Pursuant to an aspect of the invention, the preformed patterns 10 areshown positioned in a gating die 20 in order for gating to be formedin-situ between the root regions 11 of the end-to-end patterns. A lowerhalf 20 a of the gating die 20 is shown in FIG. 1. The upper half of thegating die 20 typically includes similar complementary die features thatmate or cooperate with those described below, FIG. 1B. For example, thegating die half 20 a includes portions of cavities 21 and 22 and runnerpassage 24 that are configured to receive a respective preformed pattern10. Although two patterns 10 are shown in gating die 20 in FIG. 1 forpurposes of illustration, typically in practice of the inventionadditional fugitive patterns similar to patterns 10 would be disposed inthe gating die, for example, with each pattern received in respectivecavities like cavities 21, which could located on the lefthand and/orrighthand sides of the die 20 in FIG. 1 in a manner to provide a diecavity arrangement similar to that shown in FIG. 3 where a common gatingcavity 22 resides between the pattern-receiving cavities 21. Alternatelyor in addition, additional die cavities 21, 22 could be disposed onopposite sides of FIG. 1 out of the plane of the drawing on the frontand back sides thereof. For example, the cavity 22 could extend normalto the plane of the drawing out of the front and/or back of the planewith cavities 21 extending from the cavity 22 along its length into andout of the plane of the drawing.

Each cavity 21 includes a first root-receiving cavity 21 a adapted toreceive the root region 11 with root extension 15 r and a second cavity21 b adapted to receive the airfoil 12 and the tip 13 with tip extension15 t. The root region 11 of each pattern 10 is received in closetolerance fit in the root-receiving cavity 21 a so to hold the patternin desired position in the die and to position root extension 15 r ingating cavity 22 of the gating die 20.

The second cavities 21 b can have any suitable shape. For example, thecavities 21 b may have a shape that is complementary to that of thepattern airfoil and tip regions 10 with clearance to permit each patternto be received in a respective cavity 21 b. Alternatively, the secondcavities 21 b can have a more generic shape as shown adapted to receiveand accommodate patterns having different airfoil and tip regions.

The gating die half 20 a includes portions of an injection runnerpassage 24 communicated to the gating cavity 22 and through which fluidgating material, such as molten wax, expanding foam plastic or othergating material, is introduced into the gating cavity 22 from a source25, which for purposes of illustration and not limitation may comprise asource on the injection machine, such as a tank or reservoir of moltengating material.

The extension 15 r on each root region 11 of each fugitive pattern 10resides in the gating cavity 22 of the die 20 when the root region 11 ofthe respective pattern 10 is received in the respective firstroot-receiving cavity 21 a. The root extension 15 r includes amechanical joint-forming surface 15 s, which is shown as a dovetailjoint-forming surface in FIG. 1.

In practicing a method aspect of the invention, the preformed fugitivepatterns 10 of an article to be cast are placed in the injection die 20and the fluid gating material, such as molten wax, is injected into thegating cavity 22 about and between the extensions 15 r via the runnerpassage 24 to form in-situ in the die 20 the gating 30 interconnectingthe fugitive patterns 10 in end-to-end (root-to-root) relation, FIG. 1A.The gating 30 is solidified about and between the extensions 15 r in amanner to mechanically lock each pattern 10 to the gating 30 by virtueof the wax bonding and mechanical joint therebetween. The fluid gatingmaterial may comprise the same or a different material from that of thepatterns 10. For example, the patterns 10 may comprise a particular waxblend while the gating 30 may comprise the same or a different waxblend.

In the above-described way, an embodiment of the invention can bepracticed to make a pattern assembly 50, FIG. 1A, that comprises one ormore preformed fugitive patterns 10 of an article to be cast and gating30 connected to and interconnecting the patterns 10 in end-to-endrelation. The pattern assembly 50 (called a gang by the inventors) ofFIG. 1A is removed from the opened gating die 20 and then is joined to aconventional sprue (not shown) and pour cup (not shown) to provide afinal pattern assembly for making a shell mold by the lost wax shellmold building process after the runner 54 (formed by solidified wax inrunner passage 24) is removed from the pattern assembly 50 at locationL. Fugitive patterns joined by a sprue or runner to a pour cup are shownin U.S. Pat. Nos. 4,108,931; 6,497,272 which are incorporated herein byreference.

Although FIGS. 1 and 1A illustrate interconnecting the fugitive patterns10 with their root regions 11 in end-to-end relation, the invention isnot so limited and can be used to interconnect the patterns 10 withgating in other arrangements. For example, referring to FIGS. 2 and 2A,fugitive patterns 10′ are shown interconnected to one another in amanner that the extension 15 r′ of the root region 11′ of one pattern10′ is interconnected to the extension 15 t′ of the tip region 13′ of anadjacent pattern 10′ by the gating 30′ injected in-situ in the gatingcavity 22′ of gating die 20′ (lower die half 20 a′ shown). Moreover, theextension 15 t′ of the tip region 13′ of one pattern 10′ is connected toa preformed fugitive (e.g. wax) pigtail crystal or grain starter andselector member 35′ by gating 31′ injected in-situ in gating cavity 23′provided in die 20′. The extension 15 r′ of the root region 11′ of theother pattern 10′ is captured in a gating block 32′ injected in-situ ingating cavity 27′ for the purpose of producing an attachment that can beused to connect with gating and/or support structure for combiningmultiple pattern assemblies 50′ into a mold setup to make a castingmold. The feature formed by cavity 27′ can be of various configurationsdetermined by the requirements for attaching assembly 50′ to a moldsetup.

To this end, in FIG. 2, the root region 11′ of each pattern 10′ isreceived in a root-receiving cavity 21 a′ and the tip extension 15 t′ isreceived in a tip-receiving cavity 21 c′ with the airfoil regionresiding in respective cavity 21 b′. The adjacent extensions 15 t′, 15r′ of the tip and root regions are thereby received in the common gatingcavity 22′. The extension 15 r′ of the opposite root region 11′ (lefthand root region of FIG. 2) is received in gating cavity 25′. Theextension 15 t′ of the opposite tip region 13′ (right hand tip region ofFIG. 2) is received in gating cavity 23′ as shown in FIG. 2.

The pigtail crystal or grain starter and selector member 35′ is receivedin fourth cavity 21 d′ adjacent the gating cavity 23′ of the die 20′.The preformed fugitive pigtail crystal or grain starter and selectormember 35′ is included on the pattern assembly of FIG. 2A in order tomake a shell mold for casting single crystal articles of metal or alloyas is well known. The preformed fugitive pigtail crystal or grainstarter and selector member 35′ is made by injecting molten wax or otherfugitive material in a suitable die cavity.

In practicing a method aspect of this embodiment of the invention, thepreformed fugitive patterns 10′ of an article to be cast and the pigtailcrystal or grain starter and selector member 35′ are placed in theinjection die 20′ and the fluid gating material, such as molten wax, isinjected from source 25′ into the gating cavities 22′, 23′, 27′ via therunner passages 24′ shown to form in-situ in the die 20′ the gating 30′,31′, 32′, FIG. 2A, of pattern assembly 50′. The gating 30′ is solidifiedabout and between the extensions 15 r′, 15 t′ in gating cavity 22′ in amanner to mechanically lock each pattern 10′ to the gating by virtue ofthe wax bonding and mechanical joint therebetween. Moreover, the gating31′ is solidified about the extension 15 t′ in gating cavity 23′ in amanner to mechanically lock the pattern 10′ to the pigtail crystal orgrain starter and selector member 35′ by virtue of the wax bonding andmechanical joint therebetween.

The pattern assembly 50′ of FIG. 2A is removed from the opened gatingdie 20′ and joined to the pour cup or other structural member byattaching preformed gating pieces or structural pieces typically to thegating 32′ to provide a final pattern assembly for making a shell moldby the lost wax shell mold building process after the runner 54′ (formedby solidified wax in runner passage 24′) is removed from the patternassembly 50′ at locations L′.

In practicing another method aspect of the invention illustrated in FIG.3, preformed fugitive patterns 100 of an article to be cast are placedin the injection die 200 (lower half 200 a shown) and the fluid gatingmaterial, such as molten wax, is injected from source 125 into thegating cavity 122 via the runner passage 124 to form in-situ in the die200 the gating 130 interconnecting the fugitive patterns 100 inside-by-side relation, FIG. 3A.

Pursuant to this aspect of the invention, the preformed patterns 100 areshown positioned in a gating die 200 in order for gating to be formedin-situ between extensions 115 on the root regions 111 of theside-by-side patterns. A lower half 200 a of the gating die 200 is shownin FIG. 3. The upper half of the gating die 200 typically includessimilar complementary die features (e.g. cavities 121, 122, and runnerpassage 124) that mate or cooperate with those described below.

For example, the gating die half 200 a includes portions of first andsecond pattern-receiving cavities 121 that are configured to receive thepreformed patterns 100.

Each cavity 121 includes a first root extension-receiving cavity 121 aadapted to receive the primary extensions 115 of the root regions 111 ofeach pattern and a second cavity 121 b adapted to receive the rootregion 111, airfoil region 112, and tip region 113 of the pattern 100with clearance. The primary extension region 115 of each pattern 100 isreceived in close tolerance fit in the extension-receiving cavity 121 aso to hold the pattern in desired position in the die and to position asecondary root extension 115 a in gating cavity 122 of the gating die200. The cavities 121 b can have any suitable shape as described abovefor cavity 21 b.

The gating die half 200 a includes portions of injection runner passage124 communicated to the gating cavity 122 and through which fluid gatingmaterial, such as molten wax or other gating material, is introducedinto the gating cavity 122 from a source 125 of the type describedabove.

The secondary root extension 115 a on each root region 111 of eachfugitive pattern 100 resides in the gating cavity 122 of the die 120when the primary extension region 115 of the respective pattern 100 isreceived in the respective root extension-receiving cavity 121 a. Thesecondary root extension 115 a has a mechanical joint-forming surface115 s, which is shown as a dovetail joint-forming surface in FIG. 3.

In practicing a method aspect of the invention, the preformed fugitivepatterns 100 of an article to be cast are placed in the injection die200 and the fluid gating material, such as molten wax, is injected intothe gating cavity 122 via the runner passage 124 to form in-situ in thedie 200 the gating 130 interconnecting the fugitive patterns 100 inside-by-side relation, FIG. 3A. The gating 130 is solidified about andbetween the extensions 115 a in a manner to mechanically lock eachpattern 100 to the gating 130 by virtue of the wax bonding andmechanical joint therebetween.

In this way, an embodiment of the invention can be practiced to make apattern assembly 150, FIG. 3A, that comprises one or more preformedfugitive patterns 100 of an article to be cast and gating 130 connectedto and interconnecting the patterns 100 in side-by-side relation. Thepattern assembly 150 of FIG. 3A is removed from the opened gating dieand then is joined to a runner bar that connects other patternassemblies 150 and a pour cup to provide a final pattern assembly formaking a shell mold by the lost wax shell mold building process afterthe runner 154 (formed by solidified wax in runner passage 124) isremoved from the pattern assembly 150 at location L.

In practicing still another method aspect of the invention illustratedin FIG. 4, preformed fugitive patterns 100′ of an article to be cast areplaced in the injection die 200′ and the fluid gating material, such asmolten wax, is injected from source 125′ into the gating cavities 122′,123′ via the runner passages 124′ to form in-situ in the die 200′ thegating 130′, 133′ interconnecting the fugitive patterns 100′ inside-by-side relation, FIG. 4A. In particular, the root regions 111′ ofthe patterns 100′ are interconnected by gating 130′, while the tipregions 113′ of the patterns 100′ are interconnected by the gating 133′.

Pursuant to this aspect of the invention, the preformed patterns 100′are shown positioned in a gating die 200′ in order for gating 130′ to beformed in-situ between root extensions 115 r′ and gating 133′ to beformed between the tip extensions 115 t′ of the side-by-side patterns. Alower half 200 a′ of the gating die 120′ is shown in FIG. 4. The upperhalf of the gating die 200′ typically includes similar complementary diefeatures (e.g. cavities 121′, 122′, 123′ and runner passage 124′) thatmate or cooperate with those described below.

For example, the gating die half 200 a′ includes portions ofpattern-receiving cavity 121′ that is configured to receive the patterns100′. The cavity 121′ includes a root extension-receiving cavity 121 a′adapted to receive the primary extensions 115 r′ of the root regions111′ of each pattern and a tip extension-receiving cavity 121 c′ adaptedto receive the primary extensions 115 t′ of the tip regions 113′ of eachpattern. The cavity 121′ also includes a cavity 121 b′ adapted toreceive the root region 111′, airfoil region 112′, and tip region 113′of the pattern 100′ with clearance. The primary root and tip extensions115 r′ and 115 t′ of each pattern 100′ are received in close tolerancefit in the cavities 121 a′, 121 c′ so as to hold each pattern in desiredposition in the die and to position secondary root extension 115 ra′ ingating cavity 122′ of the gating die 120′ and secondary tip extension115 ta′ in gating cavity 123′ of the gating die 120′. The secondary rootand tip extensions 115 ra′, 115 ta′ each has a mechanical joint-formingsurface 115 s′, which is shown as a dovetail joint-forming surface inFIG. 4. As described above, the cavities 121 b′ can have any suitableshape as described above for cavity 21 b.

The gating die half 200 a′ includes portions of injection runnerpassages 124′ communicated to the gating cavity 122′ and 123′ throughwhich fluid gating material, such as molten wax or other gatingmaterial, is introduced into the gating cavity 122′ and 123′ from asource 125′ of the type described above.

In practicing a method aspect of the invention, the preformed fugitivepatterns 100′ of an article to be cast are placed in the injection die200′ and the fluid gating material, such as molten wax, is injected intothe gating cavities 122′, 123′ via the runner passages 124′ to formin-situ in the die 200′ the gating 130′, 133′ interconnecting thefugitive patterns 100′ in side-by-side relation, FIG. 4A. The gating130′, 133′ is solidified about and between the extensions 115 ra′, 115ta′ in a manner to mechanically lock each pattern 100′ to the gating130′, 133′ by virtue of the wax bonding and mechanical jointtherebetween.

In this way, an embodiment of the invention can be practiced to make apattern assembly 150′, FIG. 4A, that comprises one or more preformedfugitive patterns 100′ of an article to be cast and gating 130′, 133′connected to and interconnecting the patterns 100′ in side-by-siderelation by injecting fluid gating material in the gating die to formthe gating in-situ therein. The pattern assembly 150′ of FIG. 4A isremoved from the gating die and then is joined to a runner bar thatconnects other pattern assemblies 150′ and a pour cup to provide a finalpattern assembly for making a shell mold by the lost wax shell moldbuilding process after the runner 154′ (formed by solidified wax inrunner passage 124′) is removed from the pattern assembly 150′ atlocation L′. It will be apparent that the patterns 100′ can be joined atthe root regions 111′ or at the tip regions 113 by the respective gating130′, 133′, rather than at both the root and tip regions 111′, 113′ asshown in FIG. 4.

Although certain detailed embodiments of the invention are disclosedherein, those skilled in the art will appreciate that the invention isnot limited to these embodiments but only as set forth in the followingclaims.

1. A method of making a fugitive pattern assembly, comprising forming aplurality of fugitive patterns of an article to be cast in a singlecrystal casting mold formed on the pattern assembly wherein each patterncomprises a first end and an opposite second end and a first side and anopposite second side between the first end and the opposite second end,preforming a separate fugitive member adapted to be incorporated in thesingle crystal casting mold formed on the pattern assembly, placing thepatterns in an injection die with at least two fugitive patterns placedin pattern-receiving cavities of the injection die in end-to-endrelation wherein the first end of one of the two patterns is adjacentthe second end of the other one of the two patterns in a common firstdie gating cavity and placing the fugitive member in another cavity ofthe injection die with a second die gating cavity between said fugitivemember and one of the fugitive patterns, and injecting fluid gatingmaterial into the die to form in-situ gating in said first diegatingcavity connected to said at least two fugitive patterns and in saidsecond die gating cavity connected to said fugitive member and said oneof the fugitive patterns.
 2. The method of claim 1 wherein the fugitivemember has a shape of a crystal selector member.
 3. The method of claim1 wherein the fugitive member has a shape of a crystal starter member.4. The method of claim 1 wherein the each pattern has an airfoil regionwith a root end region and a tip end region wherein the root end regionsof adjacent patterns are interconnected by the gating.
 5. The method ofclaim 1 wherein each pattern has an airfoil region with a root endregion and a tip end region wherein the root end region of one patternis interconnected to the tip end region of an adjacent pattern by thegating.
 6. The method of claim 1 including forming an extension on eachpattern such that the extension communicates to the first die gatingcavity when the pattern is received in said pattern-receiving cavity. 7.The method of claim 6 wherein the extension includes a region having amechanical joint-forming surface.
 8. The method of claim 7 wherein thejoint-forming surface comprises a dovetail joint-forming surface.
 9. Themethod of claim 1 wherein the fluid gating material comprises wax.